Sound receiver, particularly for receiving sound waves in liquids



May 12,1925 I (1,537,930

H. LICHTE SOUND'RECEIVER, PARTICULARLY FOR RECEIVING SOUND WAVlS IN'LIQUIDS FiledJan. 22, 1923 2 Sheets-Sheet 1 dizg/ May 12, 1925- H. LICHTE SOUND RECEIVER, PARTICULARLY FOR RECEIVING SOUND WAVES IN LIQUIDS Filed Jan. 22, 1923 2 Sheets-Shea} 2 HUGO LIGHTE, 0F KIEL, GERMANY, ASSIGNOR' TO SIGNAL .GESELLSCHAFT MIT BESCHRANKTER HAFTUNG, OF KIEL, GERMA-NY, A FIRM.

BOUND RECEIVER, PARTICULARLY FOR RECEIVING SOUND WAVES IN LIQUIDS.

Application filed January 22, 1923.

To all whom it may concern:

Be it known that I, HUGO LICHTE, citizen of the German Republic, and residing at Kiel, county of Schleswig-Holstein, and State of Prussia, Germany, have invented certain new and useful Improvements in Sound Receivers, Particularly for Receiving Sound Waves in Liquids, of which the following is a specification.

The invention relates to sound receivers, more particularly submarine sound receivers of the kind in which a sound receiving diaphragm cooperates with a sound detector such as a microphone. The present application is a continuation in part of my application, Ser. No. 533,005, filed January 31, 1922.

The object of the invention is to produce a sound receiver of high responsivenesswhich at the same time is sufficiently damped. Another object of the invention is to produce a receiving apparatus the resonance curve er range of which is so broad as to cover a range of frequencies from about 700 to 1300 periods per second.

The most important features of the invention are that the radiation damping of the receiver is much higher than heretofore and the coupling between the receiving diaphragm and the sound detector is loose, 40%.

The high radiation damping referred to is obtained in the receiver, according to the resent invention, by the particularly large irnensions of the diaphragm abuttin on the transmitting sound propagating medium, which dimensions far exceed the dimensions hitherto used in this classof apparatus. The invention'is equally applicable to a receiver of the so-called pressure type, in which the diaphragm abuts only on one side on the sound propagating liquid, or to a the coupling percentage not exceeding receiver of the directional type in which the diaphragm itself contains a detector and abuts on both sides on the sound propagating liquid. Whilst hitherto diaphragms having a diameter of at the most about 8 centimeters were used, the receiving ap arafusaccording to the present invention as a diaphragm having a diameter of at least 10 centimeters. Since at the same time the tunin of the diaphragm must be relatively high or submarine work, it is obvious that the thickness also of the diaphragm is con- Serial No. 614,173.

siderable. The diaphragm and the detector are each individually tuned to the same or approximately the same frequency, and so that thefrequency range covered by the resonance peaks of the coupled system of the finished apparatus agrees substantially with the range of frequencies to'be received; In submarine signaling this is generally the above-mentioned range of about 700 to 1300 cycles per second.

The second characteristic fe ture of the invention, the loose coupling tween the radiating member (receiving diaphragm) and detector, is obtained by making the mass of the detector which is connected with the radiating diaphragm very much greater than the freely vibrating mass of the detector. If, for example, it is intended tohave 20% coupling, this -means that in a case where the edge or boundary mass of the radiating diaphragm is great compared with the constructional mass of the detector 1 which is attached to th diaphragm. If the freely vibrating mass of the detector is about 5 grams, the central point mass of the diaphragm can be about 125 grams.

Further features of the invention will appear with the aid of the constructional ex amples shown in the-accompanying draw-. ing, in which,

Fig. 1 shows a sub arine sound receiver according to the inven ion in which one surface of the diaphra abuts against the water.

the directional type in which both surfaces of the receiving diaphragm abut on the water and in which the detector is enclosed in a watertight casing in the centre of the receiving dia hragm.

Figs. 3 an 4 show electromagnet detectors which may be used in place of the mi crophones shown in Figs. land 2,

And Fig. 5 shows the connection of a receiver of the kind described with a trans-- mitter of similar design.

Fig. 2 shows a submarine sound receiver of In Fig. 1, 1 indicates the casing of the receiver (shown broken away) and. 2 indicates the radiating diaphragm which is constructed with the casing from one piece of material. The diaphragm has a centrally located annular projection 3, provided with screw threads on its inner surface. Into this screw-threaded recess there is screwed an intermediate ring 4 of hard electric insulating material, which ring is also provided with interior screw threads into which the casing part 5 of the microphone is screwed. The freely oscillating mass of the microphone is the second electrode and is mounted on a diaphragm 7, which latter is secured by a pressure ring or cap 8 to the casing 5. 9 is the granular filling of the microphone while 6 is the usual ring of felt or the like. Since a relatively great'weight of the microphone is permissible in a receiver according to the invention, the sensitive part of the microphone, viz., the electrode 7, which might readily be damaged,

' is covered, together with the diaphragm 7,

by a rigid cover 10. The microphone can readily be removed as a whole from its position on the diaphragm and be replaced by another by an inexperienced person, if it becomes insensitive. Moreover, the microphones are protected by the caps during storage, transport, and assembly. *The leading-lp conductors for the microphone are designated by 11 and 12.

In Fig. 2, 13 indicates the receiving diaphragm, 14 its edge 'mass and 15 the microphone which is inserted in a central chamber 16 of the diaphragm. The microphone is secured to the diaphragm in the same manner as indicated in Fig. 1. The central diaphragm chamber is closed by a screw cover 17 with a lead washer 17". phragm itself contains a passage 18 through which the microphone leads 19 and 20 are guided. ,They are connected. to the ends of a cable, which is led in through a stuflingbox 21 so that a tight seal is formed.

- In lace of a microphone for the detector an e ectromagnetic system with movable armature or movable coil ma be used. In both cases the large mass 0 the magnetic system is connected with the radiating diaphragm of the apparatus, whilst'the small mass is connected with the large one elastically so that it 'can vibrate freely. Detectors of this 'kind are illustrated diagrammatically in Figs. 3 and 4, in which 23 represents a magnetic field. In the detector of Fig. 3, an armature 22 corresponds to the freely vibratory mass of the microphone; in the detector of Fig. 4, 'the detector is of the electrodynamic type and its freely-vibratory mass is formed by the coil 24. Both the armature 22 of Fig. 3, and the coil 24 of Fig. 4, are elastically connected to the mass attached to plate 2.

The dia-.

In Fig. 5. the detector is of the same type as that shown in Fig. 3, comprising a field 23 and an armature 22. It difiers from Fig. 3 only in thefeature that the field is of triangular form so that the poles of the field converge toward one another. In consequence of this the armature 22 may be formed shorter and thicker and at the same time of small weight. Systems ofvthis kind have distinct electromagnetic and acoustic advantages as compared with systems of the type of Fig. 3. If a receiver according to the invention, with a detector as shown in Fig. 5, is connected to a telephone transmittcr comprised in'the same electromagnetic system, a sound receiving plant is obtained having better receptive properties than the well-known microphone-telephone systems used heretofore, and at the same time the disadvantages involved in the use of batteries and the like are avoided.

The percentage-of coupling between two vibratory bodies or units, determines or is determined by. the quantity of acoustic energy which istransferred from one vibratory body or unit to the other when one is set in vibration. The percentage of coupling is the ratio of the acoustic energy so trans ferred to the amount of acoustic energy developed in the transferring body or unit when it is set in vibration. It maybe stated, that the coupling between physical vibratory bodies or units is determined exactly as in the case of electric oscillatory or vibratory circuits.

A formula for calculating the coupling between electric oscillatory circuits is given in The elementary principles of wireless telegraphy. by Bangay, Part 1. page .109, and is as follows:-lf l equals the percentage of coupling between-twocircuits. and 7., is the wave-length of the longer of the two resulting waves, 7., the wave-length of the shorter of the two resulting waves, and 1,, the wave-length of each of the circuits taken separately, then k Of course. frequency may be'subst'ituted for wave-length in the above formula.

This formula may be used for calculating or measuring the coupling between physical vibratory bodies, in accordance with the present invention, in the completed or finished acoustic apparatus. 7

A formula for calculating the coupling more or less roughly in advance will now be given, referring by way of example to Fig. 1 of the drawings. In this figure, two'individually vibratory structures are shown. One of these vibratory stnuctureshas as one of its masses the rim 1; as the elastic portion of the structure the diaphragm 2; and as the other mass, principally the X 100 (approximately).

microphone casing or body 5, the ring 4, a portion of the mass of diaphragm 2, and a mass of the sound propagating medium which vibrates in phase therewith. The other vibratory structure has as one of its masses the last-named mass (which is common to the two vibratory structures); as the elastic portion of the structure the diaphragm 7 and as the other mass principally the electrode 25. These two "ibratory structures are each individually tuned preferably to substantially the same frequency,-

and are coupled together by means of the common mass. If the three; masses of the two vibratory structures are designated in the order named as m,, m and m then the following formula will give approximately the coupling.

Among the advantages obtained by the invention are the following: On-accountof the construction of the diaphragm being very stout for the reasons explained, it is possible to construct the diaphragm and the casing of the receiver or the thickened edge or flange from one piece of material, wheretory.

by the troublesome'soldering in or screwing in of the diaphragm is obviated. The'pre viously used small diaphragms were too thin to be manufactured at the same time inone piece with the casing by casting or turning to meet satisfactorily the requirements of practice.

The unusually large size of the diaphragm in combination with its relatively high tum ing assures that'of its own accord the central point mass is great. From this there results the further advantage that the adjacent constructional masses of the detector need not be so extraordinarily light as previously was the case. The detector can therefore be made quite extraordinarily massive and heavy without the mass added to the central point mass exerting an injurious diminishing influence on the radiation damping of the diaphragm. This feature has of course for microphones the articularly important advantage that the detector can be uniformly constructed very easily and with great accuracy in the fac- The manner of securing the detector to the diaphragm shown in the figures has the further advantage that transverse non-axial movement or other disturbing oscillations of the microphone casing as a whole .are

avoided. These objections occured in the case of'previous constructions and gave rise to most unpleasant disturbances during rece tion. I

he considerations dealt with above for the detector are applicable for all kinds of detectors, whether microphone, electromagnetic or electrodynamic detectors or the like.

I claim 1. In submarine sound receiving apparatus, a tuned radiating system of high radiation damping including one member of a vibratory sound detector, and an independently vibratory structure coupled therewith, comprising another detector member the coupling between the radiating system and said independently vibratory structure being not greater than 40%.

2. Ina submarine sound receiving apparatus, a tuned radiating diaphragm of high radiation damping including one member of a vibratory sound detector, and an independent vibration system coupled therewith and tuned to substantially the same frequency as said radiating diaphragm and including another detector member, the coupling between the radiating diaphragm and said independent system being not greater than 40%.

3. In a submarine sound receiving apparatus, a tuned radiating diaphragm having a radiatingsurface diameter of at least ten centimeters and including one member of a vibratory sound detector, and an independent vibration system coupled therewith and including another detector member, the coupling beween the radiating diaphragm and said independent system being not greater than 40%.

4. In submarine sound receiving apparatus, a tuned radiating system of hi h radiation damping, and an independent y vibratory structure coupled therewith, vibratory structure being formed of two distinct masses connected by an elastic member, one mass being connected to the radiating system and vibratable therewith and the other being freely vibratable, and the mass connected to the radiating system being so much greater than the freely vibratable mass that the rate of coupling between the radiating system and said independently vibratory structure is not greater than 40%.

5. In submarine sound receiving apparatus,"a tuned radiating system of high radiation damping, and an independently vibratory structure cou led therewith, thevibratory structure being formed of two distinct masses connected by an elastic memone mass being connected to the radiatcentimeters, a relatively large rim mass boundin said diaphragm and constructed out of t e same piece of material and intothe gral with the diaphragm, and a detector comprising two distinct masses and an elastic diaphragm connecting said masses, the larger mass being rigidly connected to the receiving diaphragm.

7. A submarine sound receiving apparatus according to claim 6 in which the ratio of the freely vibratable mass of the detector to the total mass vibrating with the middle zone of the receiving diaphragm is smaller than 1 to 10.

8. In submarine sound receiving apparatus, a receiving diaphragm having a radiating surface of a diameter of at least 10 centimeters, a relatively large rim mass bounding said diaphragm and constructed out of the same piece of material and integral with the diaphragm, and a detector comprising a casing, a freely Vibratable mass and an elastic diaphragm connecting said casing and said mass, themass of the casing being larger than the freely vibratr' able mass and being rigidly connected to the receiving diaphragm. 

